Does You Coffee Smell Rancid?

Jun 8

Have you ever noticed your ground coffee smelling like fish? More specifically, freshly ground dark roasted coffee giving off a fishy odor? Don't worry! This is a fairly common issue, and I'll explain why it happens and provide solutions to diagnose and eliminate that unpleasant smell.

When was the last time you cleaned your grinder?

Depending on the type of coffee you buy (light roast vs. medium roast vs. dark roast), oils can build up in your coffee grinder, causing a rancid, fishy smell. Remove the hopper and inspect the burrs visually. Give them a sniff—you should be able to detect the fishiness immediately. The quickest cleaning solution is to use grinder cleaning tablets, but if coffee oils have heavily built up, you may need to remove the burrs entirely and soak them in rubbing alcohol or Cafiza. Always consult your grinder’s manual before doing so. (You can purchase grinder cleaning tablets and Cafiza here.)

Pro Tip: Regularly clean your grinder every 1-2 weeks if you use it daily. This prevents the buildup of oils and residue that can affect the taste of your coffee.

When was the last time you cleaned your brewing equipment?

Believe it or not, your kettle and brewing equipment (drip cone, coffee pot, etc.) need deep cleaning at least once a year. Organic and inorganic materials, such as minerals and micro-plant matter, eventually build up on your brewing equipment. This is especially true if you use a reusable coffee filter (like metal mesh cones). While these might not produce a rancid smell, they can contribute to your coffee tasting funky.

Check inside the kettle for mineral buildup, especially at the bottom. Wash your kettle with soap and water. If it has a thermometer, be careful not to damage it. Soaking the kettle in Cafiza can provide a deeper clean. Do the same with any drip cone or Chemex-style brewer.

If you use a coffee pot, inspect the water spout and the inside of the water reservoir. Clean them with soapy water, Cafiza, or run some descaler through the machine if it's not brewing correctly. Be sure to follow the manufacturer’s instructions for safe cleaning and part removal if necessary.

I prefer using Dawn dish soap, available almost anywhere. Here are links to purchase the Cafiza and descaler I use.

Pro Tip: For best results, clean your brewing equipment monthly. This not only ensures a great taste but also prolongs the lifespan of your equipment.

How old is your coffee?

Most roasters include a roast date on their coffee bags so consumers know how old the coffee is after purchase. While there is plenty of information on coffee’s shelf life, there's no definitive answer. Coffee is typically "most fresh" 1-4 weeks after the roast date and can last even longer if stored properly in an airtight container, away from sunlight. Coffee can even be stored in the freezer to preserve its taste and quality for several months.

All roasted coffees produce some type of oil from the sugars and carbohydrates that exfoliate after the roasting process. Lightly roasted coffee usually has little to no oils, but darker roasted coffee, depending on the roast degree, has more visible oils. It usually takes 24 hours for these oils to surface on the beans. After a few weeks (or even months), these oils dissipate and eventually disappear. A perfect example is Starbucks' espresso blend. Often, it’s super oily, but sometimes there are no traces of oil. This is because the coffee is usually so old that the oils evaporated or rubbed off.

There's nothing wrong with old coffee, but to preserve it without it becoming too oily, stick it in the freezer after a few weeks of opening the bag. Old coffee, especially old dark roasted coffee, can develop a "fishy" smell if it has been sitting out for too long.

Pro Tip: Store your coffee in a cool, dark place in an airtight container. Avoid keeping coffee in the fridge as the moisture can cause it to spoil faster.

Again, how old is your coffee?

Another thing to consider with old coffee is that the oils can turn rancid, producing a smell similar to fish or saltwater. This oxidation causes the oils to turn sour or rancid. While not all dark roasted coffee will develop this smell, it does happen. The sour/rancid beans aren’t bad for you, but they can cause stomach discomfort and heartburn.

Pro Tip: Store your coffee in a cool, dark place in an airtight container. Avoid keeping coffee in the fridge as the moisture can cause it to spoil faster.

How’s your water?

Brewing with good water is crucial. Depending on where you live, tap or filtered water might yield the best-tasting coffee. However, if you live in areas like the Sierra Nevadas or the Rocky Mountains, your water might come from a local spring or well, which can be better for brewing coffee due to its organic and inorganic matter.

Run a test with your filtered water and tap water. Boil both in separate bowls and let them cool to room temperature. Taste both waters to see which one tastes better. You might find that your water is causing unpleasant smells or tastes. While it's uncommon for water to smell "fishy," it is a possibility.

When I opened my roastery and tested my water, I purchased a bottle of distilled water, added 3rd Wave Water minerals, and compared its taste and smell to the municipal filtered water I use. The water at my roastery is very clean and good, so I don't need a crazy filtration system or water enhancer like 3rd Wave Water. But 3rd Wave Water is excellent for calibrating and testing the water you normally brew coffee with. Depending on where you live, consider running the same test to see how your water compares to 3rd Wave Water.

Pro Tip: If your tap water has a strong chlorine smell or taste, consider using a water filter designed to remove chlorine and other impurities.

At the end of the day, it’s just coffee 😊

Everyone's taste buds and olfactory systems are unique. Some people like dark roasts, and others don't. There's no right or wrong way to brew and drink coffee. However, maintaining and cleaning your brewing equipment properly ensures the best-tasting coffee possible.

If you're having trouble with your coffee or brewing equipment, reach out to us! We'll be happy to help.

Pro Tip: Experiment with different brewing methods and coffee beans to discover your perfect cup of coffee.

FAQs

Q: Can I use vinegar to clean my coffee equipment?
A: Yes, vinegar can be used to clean coffee equipment, especially for descaling. However, make sure to rinse thoroughly to avoid any residual vinegar taste.

Q: How often should I descale my coffee machine?
A: It's recommended to descale your coffee machine every 3-6 months, depending on the hardness of your water.

Q: Does freezing coffee beans affect their flavor?
A: Freezing coffee beans can help preserve their flavor, especially if you buy in bulk. Just make sure to store them in an airtight container to prevent freezer burn.

Craig Batory